U.S. patent application number 12/901252 was filed with the patent office on 2012-04-12 for compensation device for fluidic oscillation flow meter and compensation method using the same.
This patent application is currently assigned to KDC TECH CO., LTD.. Invention is credited to In Sung CHA, Young Geun HONG, Moon Young KIM, Hyoung Kee YANG.
Application Number | 20120089350 12/901252 |
Document ID | / |
Family ID | 45925798 |
Filed Date | 2012-04-12 |
United States Patent
Application |
20120089350 |
Kind Code |
A1 |
KIM; Moon Young ; et
al. |
April 12, 2012 |
COMPENSATION DEVICE FOR FLUIDIC OSCILLATION FLOW METER AND
COMPENSATION METHOD USING THE SAME
Abstract
Disclosed herein is a compensation device for fluidic
oscillation flow meters. The compensation device includes a fluid
supply unit, a fluidic oscillator, an electronic valve, a reference
tank and a computer. The fluid supply unit supplies fluid into a
pipe. The fluidic oscillator generates a characteristic oscillation
frequency when the fluid supplied from the fluid supply unit passes
through the fluidic oscillator. The electronic valve controls a
flow rate of the fluid passing through the fluidic oscillator. The
reference tank accumulates and stores the fluid passing through the
electronic valve. The computer calculates a characteristic linear
compensation coefficient using data about the time for which the
fluid had passed through the fluidic oscillator, an oscillation
frequency of the fluidic oscillator, a preset flow rate of the
electronic valve, and a preset fluid accumulation amount. The
computer stores the calculated characteristic linear compensation
coefficient.
Inventors: |
KIM; Moon Young; (Gunpo-si,
KR) ; HONG; Young Geun; (Gunpo-si, KR) ; YANG;
Hyoung Kee; (Gunpo-si, KR) ; CHA; In Sung;
(Gunpo-si, KR) |
Assignee: |
KDC TECH CO., LTD.
Gunpo-si
KR
|
Family ID: |
45925798 |
Appl. No.: |
12/901252 |
Filed: |
October 8, 2010 |
Current U.S.
Class: |
702/45 |
Current CPC
Class: |
G01F 15/02 20130101;
G01F 1/3227 20130101; G01F 15/005 20130101; G01F 15/003
20130101 |
Class at
Publication: |
702/45 |
International
Class: |
G01F 1/00 20060101
G01F001/00 |
Claims
1. A compensation device for fluidic oscillation flow meters,
comprising: a fluid supply unit supplying fluid into a pipe; a
fluidic oscillator generating a characteristic oscillation
frequency when the fluid supplied from the fluid supply unit passes
through the fluidic oscillator; an electronic valve controlling a
flow rate of the fluid passing through the fluidic oscillator; a
reference tank accumulating and storing therein the fluid passing
through the electronic valve; and a computer calculating a
characteristic linear compensation coefficient using data about a
time for which the fluid passes through the fluidic oscillator, an
oscillation frequency of the fluidic oscillator, a preset flow rate
of the electronic valve and a preset fluid accumulation amount, the
computer storing the calculated characteristic linear compensation
coefficient.
2. The compensation device as set forth in claim 1, further
comprising: means for controlling the fluid supply unit such that
the fluid is supplied in steps from the fluid supply unit into the
pipe; an oscillation frequency detector detecting the oscillation
frequency of the fluidic oscillator; and a level meter measuring
whether the amount of fluid accumulated in the reference tank has
reached the preset fluid accumulation amount.
3. The compensation device as set forth in claim 2, wherein the
computer comprises: a valve control unit controlling opening of the
electronic valve and the flow rate of fluid passing through the
electronic valve; a compensation coefficient calculator calculating
the characteristic linear compensation coefficient of the fluidic
oscillator; and a storage unit storing the calculated linear
compensation coefficient.
4. The compensation device as set forth in claim 1, wherein the
computer calculates the characteristic linear compensation
coefficient of the fluidic oscillator both from a flow rate for a
predetermined unit time and the oscillation frequency of the
fluidic oscillator, the flow rate for the predetermined unit time
being determined by the time for which fluid had passed through the
fluidic oscillator, the preset flow rate of the electronic valve
and the preset fluid accumulation amount of the reference tank.
5. A compensation method of a fluidic oscillation flow meter,
comprising: supplying fluid from a fluid supply unit into a pipe;
detecting an oscillation frequency using an oscillation frequency
detector when the fluid supplied from the fluid supply unit passes
through a fluidic oscillator, and transmitting the detected
oscillation frequency to a computer; controlling the fluid using an
electronic valve such that the fluid passing through the fluidic
oscillator passes through the electronic valve at a preset flow
rate; accumulating and storing the fluid passing through the
electronic valve in a reference tank; checking the amount of fluid
accumulated in the reference tank using a level meter, and
transmitting a detection signal to the computer when the amount of
accumulated fluid reaches a preset fluid accumulation amount;
receiving the detection signal from the level meter using the
computer and turning off the electronic valve; checking, a time for
which fluid had passed through the fluidic oscillator, the preset
flow rate of the electronic valve, and the preset fluid
accumulation amount of the reference tank using the computer, and
then calculating a flow rate for a predetermined unit time;
calculating a characteristic linear compensation coefficient of the
fluidic oscillator based on the oscillation frequency generated
when fluid passes through the fluidic oscillator; and storing the
calculated characteristic linear compensation coefficient of the
fluidic oscillator in a storage unit.
6. The compensation method as set forth in claim 5, wherein in the
electronic valve, the flow rate is subdivided per a unit flow rate
into steps from a basic flow rate to a critical expected maximum
flow rate, and a characteristic linear compensation coefficient of
the fluidic oscillator is calculated at each step and stored in the
storage unit.
7. The compensation method as set forth in claim 5, wherein when
the flow meter including the fluidic oscillator is manufactured,
the computer refers to the characteristic linear compensation
coefficients of the fluidic oscillator which are calculated based
on the oscillation frequency of the fluidic oscillator and stored
in the storage unit and then applies a corresponding characteristic
linear compensation coefficient to the flow meter.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates generally to compensation
devices and methods for fluidic oscillation flow meters and, more
particularly, to a compensation device and method for a fluidic
oscillation flow meter which compensates both for inconsistencies
in the measured values due to the characteristics of the fluidic
oscillation flow meter used to measure a flow rate of fluid and for
inconsistencies in the measured values attributable to the
deformation of a mold which may be induced when conducting an
injection molding process to produce a fluidic oscillator used to
implement fluidic oscillation.
[0003] 2. Description of the Related Art
[0004] With regard to flow meters using oscillation of fluid jets
to measure flow rates, fluid discharged from a jet drops in
pressure when it comes out of the outlet of the jet. Due to the
dropped pressure, the fluid is attracted to a nearby surface and
flows along the surface. This phenomenon is called the "Coanda
effect".
[0005] If a path is provided for the fluid such that some of the
fluid which flows along the nearby surface because of the Coanda
effect is guided along the fluid path towards the outlet of the
jet, the fluid thus flowing along the nearby surface collides with
fluid which is flowing forwards thereby impeding advancement of the
discharged fluid. Thereby, the fluid jet oscillates. A period of
the oscillating fluid jet is proportional to the flow rate of
fluid. Hence, the flow rate of the fluid can be determined using
the ratio of it to the period. This principle is called "fluidic
oscillation". A structure manufactured using the fluidic
oscillation principle is called a "fluidic oscillator".
[0006] The fluidic oscillator includes a jet nozzle which forcibly
discharges fluid, a feedback channel through which discharged fluid
reduced in pressure flows towards the jet nozzle along the nearby
surface due to the Coanda effect, and an obstacle which promotes
oscillations in the discharged fluid.
[0007] To analyze the period of oscillation of fluid with respect
to the flow rate, the fluid must have a regular laminar flow.
Reynolds number analysis is used to discern whether the flow of
fluid is in the regular state or not. A boundary value at which the
flow of fluid changes from laminar to turbulent is called the
"critical Reynolds number". Even though a fluidic oscillator should
be designed such that the laminar flow of fluid is stably
maintained, a fluidic oscillator which is over the critical value
may be manufactured depending on conditions (pressure, temperature,
humidity, etc.) present during the injection molding process. In
this case, there is a problem because despite the fluid passing
through the fluidic oscillator at the same flow rate, the results
may differ.
[0008] Furthermore, because of some characteristics of the flow
meter using the above-mentioned fluidic oscillation, when the flow
rate of fluid passing through the flow meter linearly varies,
oscillation frequency of the fluid is also changed depending on
variations in the flow rate. Thus, the measured data is detected as
non-linear rather than having a constant proportional value.
[0009] Therefore, a fluidic oscillation flow meter and a method are
required, which are capable of correctly measuring the flow rate of
fluid despite the problem induced by the characteristics of the
fluidic oscillator which may be over the critical value and despite
variations in oscillation frequency of fluid depending on
variations in the flow rate.
SUMMARY OF THE INVENTION
[0010] Accordingly, the present invention has been made keeping in
mind the above problems occurring in the prior art, and an object
of the present invention is to provide a compensation device and
method for a fluidic oscillation flow meter which compensates both
for inconsistencies in the measured values due to the
characteristics of the fluidic oscillator used in the flow meter
and for inconsistencies in the measured values attributable to
variations in the oscillation frequency of a fluid depending on
variations in the flow rate, thus making it possible to
consistently measure the flow rate of a fluid.
[0011] In order to accomplish the above object, the present
invention provides a compensation device for a fluidic oscillation
flow meter including: a fluid supply unit having a fluid tank and a
pump which supplies fluid into a pipe for implementing fluidic
oscillation and controls the flow rate of the fluid in steps; a
fluidic oscillator for measuring the flow rate of fluid passing
through the pipe; an oscillation frequency detector detecting the
oscillation frequency when fluid passes through the fluidic
oscillator; an electronic valve controlling the flow of fluid
through the pipe; an electronic valve controller controlling the
operation of the electronic valve; a reference tank accumulating
and storing fluid that has arrived through the electronic valve; a
level meter checking the amount of fluid accumulated in the
reference tank; a computer having a valve control unit, a
compensation coefficient calculator, a storage unit and a control
unit. The valve control unit receives a signal telling of the
amount of accumulated fluid checked by the level meter and
transmits an interruption signal to the electronic valve
controller. The compensation coefficient calculator receives data
about the amount of accumulated fluid in the reference tank checked
by the level meter, a time for which the accumulated fluid passes
through the fluidic oscillator, and the oscillation frequency of
the fluidic oscillator measured by the oscillation frequency
detector and then calculates a characteristic linear compensation
coefficient of the fluidic oscillator. The storage unit combines
the characteristic linear compensation coefficient calculated by
the compensation coefficient calculator with data of the fluidic
oscillator and stores the combined data. The control unit controls
the compensation coefficient calculator and the valve control
unit.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The above and other objects, features and advantages of the
present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0013] FIG. 1 is a block diagram showing the construction of a
compensation device for a fluidic oscillation flow meter, according
to an embodiment of the present invention; and
[0014] FIG. 2 is a flowchart of an embodiment of a compensation
method of the fluidic oscillation flow meter according to the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] Hereinafter, an embodiment of the present invention will be
described in detail with reference to the attached drawings.
[0016] A fluidic oscillator used in a fluidic oscillation flow
meter will be explained to more clearly understand the embodiment
of the present invention. When the fluidic oscillator is formed by
injection molding, the portion that forms the fluid jet may be
formed in an incorrect and not the desired shape. In this case, the
number of oscillations of fluid according to a flow rate becomes
different from existing data obtained from tests of fluidic
oscillators. Thus, a lot of errors occur when measuring the flow
rate. It has been known that when a flow rate of fluid is measured
by such a fluidic oscillator, as the flow rate of fluid is low, the
precision thereof is reduced.
[0017] A critical Reynolds number at which the flow of fluid
changes from laminar to turbulent ranges from about 2000 to about
2800 or more. An equation for measuring the flow rate when the flow
of fluid changes from laminar to turbulent is as follows:
stable Reynolds number < critical Reynolds number = flow rate
kinematic viscosity .times. pipe diameter ##EQU00001##
[0018] In the above equation,
[0019] When the critical Reynolds number=2500,
[0020] kinematic viscosity=1.007.times.106 m'/s, and
[0021] diameter of a typical domestic water supply pipe=15 mm,
[0022] the flow rate is about 0.136 m'/h. From this, it can be
understood that turbulence occurs when the flow rate is 0.136 m' or
less per an hour. Furthermore, it is well known that when a
cross-section area of the portion of the fluidic oscillator that
forms a fluid jet varies by 0.01 inch, the generated oscillation
frequency differs widely.
[0023] FIG. 1 is a block diagram showing the construction of a
compensation device for a fluidic oscillation flow meter, according
to an embodiment of the present invention.
[0024] As shown in FIG. 1, the compensation device for the fluidic
oscillation flow meter according to the present invention includes
a fluid supply unit 100, a fluidic oscillator 200, an oscillation
frequency detector 210, an electronic valve 300, an electronic
valve controller 310, a reference tank 400, a level meter 410 and a
computer 500. The fluid supply unit 100 includes a fluid tank 110
and a pump 120 which supplies fluid through a pipe to the fluidic
oscillator 200 for implementing fluidic oscillation and controls
the flow rate of the fluid in steps. The fluidic oscillator 200 is
used to measure the flow rate of fluid passing through the pipe.
The oscillation frequency detector 210 detects the oscillation
frequency when fluid passes through the fluidic oscillator 200. The
electronic valve 300 controls the flow of fluid through the pipe,
and the electronic valve controller 310 controls the operation of
the electronic valve 300. The reference tank 400 is provided with a
level gauge and accumulates and stores fluid that has arrived
through the electronic valve 300. The level meter 410 checks the
amount of fluid accumulated in the reference tank 400. The computer
500 includes a valve control unit 510, a compensation coefficient
calculator 520, a storage unit 530 and a control unit 540. The
valve control unit 510 receives a signal telling of the amount of
accumulated fluid checked by the level meter 410 and transmits an
interruption signal to the electronic valve controller 310. The
compensation coefficient calculator 520 receives data about the
amount of accumulated fluid in the reference tank 400 checked by
the level meter 410, a time for which the accumulated fluid passes
through the fluidic oscillator, and the oscillation frequency of
the fluidic oscillator 200 measured by the oscillation frequency
detector 210 and then calculates a characteristic linear
compensation coefficient of the fluidic oscillator 200. The storage
unit 530 combines the characteristic linear compensation
coefficient calculated by the compensation coefficient calculator
520 with data of the fluidic oscillator 200 and stores the combined
data. The control unit 540 controls the compensation coefficient
calculator 520 and the valve control unit 510.
[0025] Fluid which is an object to be measured and has been
contained in the fluid tank 110 is transferred to the pipe by the
operation of the pump 120. When fluid which is transferred through
the pipe passes through the fluidic oscillator 200, the fluid
oscillates and a characteristic oscillation frequency is generated
in response to the flow rate of the fluid. The oscillation
frequency detector 210 measures the oscillation frequency generated
in the fluidic oscillator 200 and sends a signal containing the
measurement to the compensation coefficient calculator 520 of the
computer 500. Fluid which has passed through the fluidic oscillator
200 is controlled by the electronic valve 300 such that it passes
through the electronic valve 300 at a preset flow rate. After the
fluid has passed through the electronic valve 300, it is
accumulated and stored in the reference tank 400. The level meter
410 checks the amount of fluid accumulated in the reference tank
400. When the amount of accumulated fluid reaches a preset volume,
the level meter 410 sends a corresponding signal to the computer
500. According to the signal transmitted from the level meter 410,
the valve control unit 510 of the computer 500 sends a signal for
turning off the electronic valve 300 to the electronic valve
controller 310. Then, the electronic valve 300 is turned off under
the control of the electronic valve controller 310. After the
electronic valve 300 is turned off, the compensation coefficient
calculator 520 calculates a characteristic linear compensation
coefficient of the fluidic oscillator 200 according to a control
signal of the control unit 540 of the computer 500 and then stores
the result in the storage unit 530.
[0026] For example, a tank having a capacity of 100 l and an MPE
(maximum permissible error) of .+-.0.2% may be used as the
reference tank 400.
[0027] With regards to calculating of the characteristic linear
compensation coefficient of the fluidic oscillator 200, the flow
rate per a predetermined unit of time is calculated from a time for
which fluid had passed through the fluidic oscillator 200.
Calculating the coefficient also takes into account the flow rate
preset in the electronic valve 300 and the amount of accumulated
fluid preset for the reference tank 400. A characteristic linear
compensation coefficient of the fluidic oscillator 200 is
calculated both from the calculated flow rate per a predetermined
unit of time and from a fluidic oscillation frequency generated
when fluid passes through the fluidic oscillator 200.
[0028] As the flow rate is increased by 0.001 m'/h in steps from
the minimum flow rate to the critical flow rate, a characteristic
linear compensation coefficient of the fluidic oscillator 200 is
calculated at each step by the above-mentioned method. The
calculated characteristic linear compensation coefficients are
stored in the storage unit 530.
[0029] In the same manner, as the flow rate is increased by 0.1
m'/h in steps up to the overload flow rate of the 15 mm standard
water meter according to the OIML (International Organization of
Legal Metrology), a characteristic linear compensation coefficient
of the fluidic oscillator 200 is calculated at each step by the
above-mentioned method
[0030] When the flow meter including the fluidic oscillator 200 is
assembled, a characteristic linear compensation coefficient
corresponding to a characteristic oscillation frequency of the
fluidic oscillator 200 is found from the storage unit 530 and
applied to the flow meter.
[0031] The process of calculating a characteristic linear
compensation coefficient of the fluidic oscillator 200 will be
explained in more detail.
[0032] For example, in the case of a general domestic water supply
pipe having a size of 15 mm, when the basic oscillation period is
1000 msec (the time for which oscillation occurs once a second) a
flow rate becomes about 0.06 m'/h which is within a nonlinear
distribution range less than 50% of the 0.135 m'/h which is the
flow rate at the critical. Reynolds number.
[0033] In other words, based on the flow rate of the basic
oscillation period being 0.06 m'/h, the nonlinear distribution of
the flow rate is subdivided by 0.001 m'/h in steps both to a flow
rate of 0.016 m'/h (the minimum flow rate of the 15 mm standard
water meter of the OIML, which is less than the flow rate of the
basic oscillation period), up to the critical expected maximum flow
rate of 0.135 m'/h. An oscillation period is measured at each step.
When the time taken to charge a predetermined amount of fluid into
the reference tank is divided by the oscillation period, the number
of oscillations which are generated while the predetermined amount
of fluid is charged into the reference tank is calculated.
[0034] A linear compensation coefficient is obtained by dividing
the amount of fluid that has been charged into and accumulated in
the reference tank by the calculated number of oscillations
[0035] Linear compensation coefficients corresponding to the steps
from the minimum flow rate to the critical expected maximum flow
rate are determined by the above-mentioned method. With reference
to the flow rate when it is over the critical expected maximum flow
rate, linear compensation coefficients are calculated in the same
manner in units of 0.1 m'/h in steps to 2.5 m'/h which is the
overload flow rate of the 15 mm standard water meter of OIML.
[0036] The fluidic oscillator can have a stable linear compensation
coefficient which is within an MPE of .+-.5% below the expected
critical flow rate of the 15 mm standard water meter, and which is
within an MPE of .+-.2% above the expected critical flow rate of
the 15 mm standard water meter. Therefore, the present invention
can minimize the rate of defectives attributable to deformation
when forming the fluidic oscillator by injection molding.
[0037] FIG. 2 is a flowchart of an embodiment of a compensation
method of the fluidic oscillation flow meter according to the
present invention.
[0038] In the compensation method of the present invention, at step
S100, fluid is supplied from the fluid supply unit into the pipe.
At step S102, the oscillation frequency detector detects an
oscillation frequency generated when fluid supplied from the fluid
supply unit passes through the fluidic oscillator. At step S104,
the oscillation frequency detected by the oscillation frequency
detector is transmitted to the computer. At step S106, fluid which
has passed through the fluidic oscillator is controlled such that
it passes through the electronic valve at a flow rate preset by the
electronic valve. At step S108, fluid which has passed through the
electronic valve accumulates and is stored in the reference tank.
At step S110, the level meter checks the amount of fluid
accumulated in the reference tank, and when the amount of
accumulated fluid reaches a preset amount, the level meter detects
that and transmits a corresponding detection signal to the
computer. At step S112, the computer receives the detection signal
from the level meter and turns off the electronic valve. At step
S114, the computer checks the time for which fluid had passed
through the fluidic oscillator, the preset flow rate of the
electronic valve and the preset fluid accumulation amount of the
reference tank and thus calculates the flow rate for a
predetermined unit time. At step S116, the computer calculates a
characteristic linear compensation coefficient for the fluidic
oscillator based on the oscillation frequency generated when the
fluid passes through the fluidic oscillator. At step S118, the
computer stores the calculated characteristic linear compensation
coefficient of the fluidic oscillator in the storage unit.
[0039] Furthermore, in the compensation method of the flow meter of
the present invention, in the electronic valve, the flow rate is
subdivided by the unit flow rate in steps from the basic flow rate
up to the critical expected maximum flow rate, and a characteristic
linear compensation coefficient of the fluidic oscillator is
calculated at each step and stored.
[0040] When the flow meter including the fluidic oscillator is
manufactured, the computer refers to the characteristic linear
compensation coefficients of the fluidic oscillator which are
calculated based on the oscillation frequency of the fluidic
oscillator and stored in the storage unit and then applies a
corresponding characteristic linear compensation coefficient to the
flow meter.
[0041] As described above, a compensation device and method for a
fluidic oscillation flow meter according to the present invention
can compensate both for inconsistencies in the measured values due
to the characteristics of a fluidic oscillator used in the flow
meter and for inconsistencies in the measured values attributable
to variations in the oscillation frequency of fluid depending on
variations in the flow rate. Therefore, the present invention makes
it possible to consistently measure the flow rate of fluid.
[0042] Although the preferred embodiment of the present invention
has been disclosed for illustrative purposes, those skilled in the
art will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as disclosed in the accompanying
claims.
* * * * *